1. Field of the Invention
The present invention relates to an electrode plate unit for a rechargeable battery and a manufacturing method of same.
2. Description of the Related Art
Batteries are classified into primary batteries and secondary batteries or rechargeable batteries, and there are various configurations for each of these two types of battery. For instance, the sealed alkaline rechargeable battery 41 shown in FIG. 12 is structured such that positive electrode plates and negative electrode plates are stacked with separators in between them to form an electrode plate unit 47 that constitutes elements for electromotive force, which is housed in a battery case 42 along with electrolyte. The opening in the battery case 42 is closed off with a lid 46 provided with a safety vent 45. Leads 49 extend upward from the top on one side of the positive electrode plates that make up the electrode plate unit 47, and a positive electrode terminal 43 is connected to the upper portion of these leads. Similarly, leads 49 extend upward from the top on the other side of the negative electrode plates, a negative electrode plate terminal 44 is connected to the upper portion of these leads, and the positive electrode terminals 43 and negative electrode plate terminals 44 are attached to the lid 46.
As shown in FIG. 13, the positive and negative electrode plates in the above-mentioned electrode plate unit 47 are integrally joined together at welds 50 in the leads 49 extending from the electrode plates. As disclosed in Japanese Laid-Open Patent Application H7-220715, for example, laser welding can be used to advantage in this welding. That is because, with resistance welding, impurities or an oxidation film at the place being welded can generate sparks, resulting in a weak weld or preventing a uniform weld from being obtained. One particularly favorable method involves passing a laser beam through the leads to form a through-hole, and then filling in this through-hole with thermally sprayed metal and re-solidifying the molten metal to obtain an integrated weld.
With the conventional battery 41 described above, the leads 49 extend from the top on one side of the electrode plates and are welded together, and the electrode terminals 43 and 44 are connected, so the average distance from the overall surface of the electrode plates to the collector portion of the leads 49 is long, and this is a problem in that the internal battery resistance is higher and the electrode active material utilization is lower, so the output of the battery is also lower.
In view of this, there is proposed a new structure for the electrode plate unit of a battery in which collector plates are disposed opposite from and abutting on both side surfaces of the electrode plate unit, and the lateral edges of the electrode plates and the collector plates are integrally welded. However, when simple seam welding is employed to integrally connect the collector plates and the lateral edges of the electrode plates, it is difficult to obtain a good connection and a poor joining state results, the problems with which are inadequate battery output and insufficient weld strength. Another problem is that even with laser welding it is exceedingly difficult to join the components securely without having a detrimental effect on the electrode plates, and there has been a need for a method for properly joining collector plates to the lateral end edges of the electrode plate unit.
In light of the above problems encountered in the past, it is an object of the present invention to provide an electrode plate unit for a rechargeable battery in which the collector plates are securely joined to either side surface of the electrode plate unit, and a method for manufacturing same.
To achieve the above object, the present invention provides a battery comprising:
an electrode plate unit, including a plurality of positive electrode plates and a plurality of negative electrode plates that are alternately stacked upon one another with intervening separators therebetween, thereby constituting respective groups of positive and negative electrode plates, wherein lateral edges of the positive electrode plates protrude beyond the negative electrode plates on one side, and lateral edges of the negative electrode plates protrude beyond the group of positive electrode plates on the opposite side;
collector plates arranged respectively on the lateral edges of the positive and negative electrode plates; and
thermal spray metal coatings formed on end surfaces of said respectively protruded lateral edges of the positive and negative electrode plates for integrally joining the positive electrode plates together and the negative electrode plates together, respectively, and for connecting respective collector plates to the positive electrode plates and the negative electrode plates.
The thermal spray coating provides secure connections between the electrode plates and the collector plates, whereby a battery with less internal resistance and higher battery output can be obtained.
Other and further objects, features and advantages of the invention will be apparent more fully from the following description.